<!DOCTYPE html>
<html>
<head>
<!-- specifying all heights in em units so that large font sizes
     don't disrupt relationships; everything will scale together -->
<style type="text/css">
#parent {
 width: 200px;
 background-color: lightgreen;
}
#inline-block1, #inline-block2 {
 height: 2em;
 background-color: green;
}
#margin {
 height: 2em;
}
</style>
</head>
<body>
<div id="parent">
 <div id="inline-block1"></div>
 <div id="margin"></div>
 <div id="inline-block2"></div>
</div>
</body>
</html>
